This invention relates to colorimetric analyzers, and more particularly to an analyzer for automatically and sequentially delivering a plurality of reagents and providing for time delays to allow reactions of the reagents with the sample to go to completion.
Colorimetric analyzers are extensively used in laboratory and industrial work to determine the constituents of a sample mixture. For example, colorimetric analysis is used to determine water hardness, to test for orthophosphate content and to test for silica in a sample.
U.S. Pat. No. 3,028,225, issued Apr. 3, 1962 to Robert T. Sheen describes a colorimetric analyzer in which the light source is divided into two beams, one of which passes through a test sample to a first photocell, and the other of which falls on a second photocell. The Sheen system includes two stopcocks which are continuously driven by a motor. These two stopcocks respectively deliver reagent and sample to a precise volume chamber. At periodic times, the precise volume is delivered to a sample cell where a continuous measurement of light transmitted through the sample is made.
Automatic chemical analyzers of this type are important because they do not require the constant attention of a technician to obtain accurate measurements. Improvement on this type of apparatus is needed in respect to providing flexibility of adding more than one reagent and in respect to allowing the reactions to go to completion before measurements are made.